This invention is a method of electrically wiring a row of semiconductor lasers and the row of lasers wired by this method.
Semiconductor lasers, like all discrete or integrated semiconductors, are produced in groups on wafers which are then snapped into bars, the snapping operation being designed to expose the two cut faces of the Fabry-Perot cavity in a laser. The bars themselves are then snapped either into individual laser chips or into smaller bars forming, for example, a row of 10 to 30 lasers. Such a row of lasers provides greater optical power but distributing electrical current to them can be a problem.
FIG. 1 is a longitudinal cross-section of a row of lasers according to the prior art. Semiconductor body 1 comprises a substrate and a number of semiconductor layers which need not be detailed here: the aim of the structure is to create laser emitter zones 2 which, when suitably polarized, emit light.
A metal support 3, to which the row of lasers is brazed, can form the first electrical terminal, for example the ground.
The second electrical terminal is on the top face of the row, i.e. that opposite the support so that the electric current flows through the laser emitter zones 2. Two methods of applying the current to this top face are known to the prior art. Either a metal film 4 is deposited, but there is then a risk of a break in the film at 5, on the edges, or there can be areas of shade since the laser zones 2 are separated by grooves 6 to channel the current vertically. Alternatively, small metallized areas 7 are deposited only on those parts of the top face which lie above the laser emitters 2 and 25 .mu.m diameter gold wires 8 are then attached to these metallized areas 7 by thermocompression brazing. Electric current is fed to the lasers individually.
These individual solutions present at least two disadvantages:
they provide virtually no thermal dissipation, even though lasers generate considerable heat,
the length of the gold wires varies depending on the position of the individual lasers to which they are connected and these different lengths cause inequality in the voltages applied.